A DbConnection is not necessarily connected.
In the case of Pyrseas dbtoyaml </dbtoyaml> and yamltodb
</yamltodb>, it will typically connect to the database when
the ~pyrseas.dbobject.DbObjectDict~pyrseas.dbobject.DbObjectDict.fetch method is first
invoked. It is normally disconnected just before the
~pyrseas.database.Database~pyrseas.database.Database.from_catalog returns.